1. Field of the Invention
This invention relates to a process for producing a carotenoid emulsion.
2. Statement of Related Art
Carotenoids are broadly present in nature, and widely used as colorants for food, etc. utilizing the characteristic that they have yellow to red color. Some carotenoids are also known to show provitamin A activity, cancer-inhibiting effect or the like, and are a compound group drawing attention also from a pharmacological viewpoint. Many isomers are present in carotenoids based on many carbon-carbon double bonds which they possess, and when a use as colorants or a use as a physiologically active agent such as a provitamin A active agent is considered, carotenoids having a high trans-form proportion are preferred.
Carotenoids are compounds which are in a crystalline state at ordinary temperature and have a high melting point, are insoluble in water, extremely low in solubility in organic solvents or fats and oils, and, moreover, tend to be isomerized with heat, and tend to be readily denatured with oxygen or light. Therefore, when it is intended to use carotenoids as colorants for food or a physiologically active agent, they need to be processed into stable and readily utilizable forms. As one process for it, there is a process of producing an emulsion of a carotenoid by mixing the carotenoid into fats and oils and then emulsifying the mixture in an aqueous solution.
Known processes of producing an emulsion of a carotenoid include (1) a process of producing a carotenoid preparation by producing, at 100 to 160xc2x0 C., a supersaturation solution of a carotenoid in an edible oil which is liquid at about 20 to 40xc2x0 C. and emulsifying this supersaturation solution into an aqueous gelatin substance (see U.S. Pat. No. 2,861,891), (2) a process of producing a xcex2-carotene preparation having a high trans-form proportion by heating trans-form xcex2-carotene, fats and oils and limonene to make a solution, recovering the limonene and converting the resulting oil layer dissolving the trans-form xcex2-carotene to an emulsion in the presence of an emulsifier (see Japanese Laid-open Patent Publication No. 8-119933), (3) a process of contacting a suspension of a carotenoid in a high boiling oil with superheated steam for maximum 30 seconds and emulsifying the resulting mixture in an aqueous solution of colloid (see Japanese Laid-open Patent Publication No. 3-66615), (4) a process of rapidly dissolving a carotenoid, together with an edible oil of 1.5 to 20 times the mass of the carotenoid and an emulsifier, in a volatile organic solvent miscible with water, at a temperature of 50 to 240xc2x0 C., then immediately mixing the resulting solution with an aqueous solution of protective colloid at a temperature of 0 to 50xc2x0 C. to move the hydrophilic solvent components into the aqueous phase and at that time change the hydrophobic oil phase containing and dissolving the carotenoid to a fine dispersion phase (see Japanese Laid-open Patent Publication No. 63-196242), and (5) a process of feeding a suspension of a carotenoid in an organic solvent immiscible with water into a heat exchanger for a residence time of less than 5 seconds to heat the suspension to 100 to 250xc2x0 C., rapidly mixing the resulting solution with an aqueous solution of easy to swell colloid at a temperature in the range of 20 to 100xc2x0 C., and then removing the organic solvent (see Japanese Laid-open Patent Publication No. 2000-186224).
The process of the above (1) is economically disadvantageous because the visible absorption spectrum of the obtained carotenoid dry powder gets low, and for example in the case of coloring of food, the use quantity of the carotenoid dry powder needs to be increased to obtain a desired value of color strength. The process of the above (2), wherein limonene is used in view of inhibiting isomerization of trans-form xcex2-carotene when the trans-form xcex2-carotene is heated for dissolution, has the problems that the same quantity or more of the limonene as that of the fat or oil needs to be used and further that since limonene is not needed in the final product, a step to remove it is indispensable. The process of the above (3) has the problems that it needs expensive apparatuses because superheated steam being in high temperature and high pressure is used and further that since water originating in the superheated steam, in addition to the water contained in the aqueous solution of colloid, joins the resulting emulsion, when the production of carotenoid powder from the emulsion is intended, a large quantity of water needs to be removed. The processes of the above (4) and (5) have the problems that since the used organic solvent is unnecessary for the final product, it needs to be removed and that use of a large quantity of the organic solvent is needed, which lowers productivity. Therefore, it is hard to say that any of these processes are industrially advantageous production process.
Thus, the object of the invention lies in providing a process capable of producing an emulsion containing a carotenoid as an effective ingredient with the carotenoid maintaining a high total trans-form proportion, with good productivity, conveniently, and industrially advantageously.
The present inventors have made intense researches for accomplishing the above object. As a result, we found that, in steps of producing a carotenoid emulsion, by using a process of passing a suspension of a carotenoid in a high boiling organic liquid, in a short time, through a conduit having a particular pipe diameter heated to a temperature in a particular range, or a process of mixing the suspension, in a short time, with a high boiling organic liquid (preferably the same kind of a high boiling organic liquid as used in preparation of the suspension) heated to a particular temperature range, it is possible to give a large quantity of heat to the suspension in a short time and dissolve the carotenoid in the high boiling organic liquid with inhibition of isomerization of the carotenoid, and by using a process of immediately emulsifying the resulting solution, it is possible to produce a carotenoid emulsion not containing any organic solvent and a large quantity of water unnecessary for final products. We further found that carotenoid powder obtained by spray drying a carotenoid emulsion obtained by such a process or by stirring the carotenoid emulsion in a nonpolar solvent to make the emulsion particles, and filtering and drying the particles can be used as colorants for food or a physiologically active agent, and completed the invention.
Namely, the present invention relates to
{circle around (1)} a process for producing a carotenoid emulsion which comprises heating a suspension of the carotenoid in a high boiling organic liquid (hereinafter, sometimes merely abbreviated as xe2x80x9ccarotenoid suspensionxe2x80x9d ), by passing the suspension through a conduit of 0.1 to 50 mm inside diameter heated to temperature in the range of 120 to 700xc2x0 C. for a residence time of 0.05 to 5 seconds or by mixing the suspension with a high boiling organic liquid heated to the range of 120 to 500xc2x0 C. for a time of 0.05 to 10 seconds, to dissolve the carotenoid, and then immediately adding the resulting solution into an aqueous solution of an emulsifier to emulsify the solution, and
{circle around (2)} carotenoid powder obtained by spray drying the resulting carotenoid emulsion or by stirring the carotenoid emulsion in a nonpolar solvent to make the emulsion particles, and filtering and drying the particles.